1. Field of the Invention
The present invention relates in general to a method of making a slider for use in a slide fastener, and more particularly to a method of making a slider for use in a slide fastener, which slider is provided with bearings for a pull tab on an upper surface of a slider body on its opposite sides to pivotably hold a pintle of the pull tab between the respective bearings for the pull tab, and which method can mold the slider body and the pull tab in an assembled state by one effort.
2. Description of the Prior Art
The technique of molding a slider body and a pull tab in an assembled state by one effort has been disclosed in the specification of Japanese Pat. application No. 63-13324 (which corresponds to U.S. Pat. No. 4,790,973 issued on Dec. 13, 1988) filed previously (on Jan. 23, 1988) by the Assignee of this U.S. patent application. According to the technique disclosed in the specification of the above-referred prior patent application, a slider body mold cavity and a pull tab mold cavity are provided in continuation within a mold, a pair of slide cores are inserted into the continuing portion between the respective mold cavities to sever the respective mold cavities, then at first an amount of molten material is injected into the slider body mold cavity to mold a slider body and also integrally mold an arch-shaped post elongated in the front and rear directions on the upper surface of the slider body, and at that time a hollow space under the arch-shaped post is formed by both the slide cores. Subsequently, one of the slide cores is retreated to form a mold portion of a pintle of a pull tab which passes through the hollow space under the already molded arch-shaped post in continuation with the pull tab mold cavity, then an amount of molten material is injected into the pull tab mold cavity to mold the pull tab having the aforementioned pintle, and thereby a slider is manufactured.
Here, it is to be noted that the reason why a pair of slide cores must be use in the above-mentioned method in the prior art is because it is necessary to form the pintle of the pull tab thinner than the cross-section area of the hollow space under the arch-shaped post so that the pintle of the pull tab can pass through the hollow space and moreover can be freely moved back and forth and rotated within the hollow space. Accordingly, at the time point when the slider body is molded, a hollow space having a sufficiently large cross-section area under the arch-shaped post is molded by making use of the both slide cores, and subsequently, by retreating one of the slide cores, a relatively thin pintle of a pull tab having a cross-section area corresponding to that of the retreated slide core is molded. Therefore, the use of a pair of slide cores is essentially necessary. However, due to the use of a pair of slide cores, a high degree of precision is required for the tightness of fitting between the respective slide cores and between the slide cores and the mold members, moreover as the number of the slide portions is increased, the structure of the mold members becomes complicated, and to say nothing of the production of mold members, there was a problem that a production efficiency of molded products was degraded.